JP3350829B2 - Rust prevention coated PC strand and its rust prevention processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rust-preventive coating method for a PC strand used mainly as a stress-introducing material for prestressed concrete (hereinafter referred to as PC) or as a suspension material for a cable-stayed bridge.

[0002]

2. Description of the Related Art In recent years, the outer surface of a PC strand is coated with a synthetic resin material having an adhesive property, and this is inserted into a synthetic resin sheath to be used for a post-tension unbonding method or a synthetic resin coating. A material used for a pre-tension bond method of embedding in a concrete after tensioning the material has been developed (Japanese Patent Laid-Open No. 1-215528).
No.).

[0003] Even if such a conventional PC strand is coated with a synthetic resin, there is a gap between the core wire constituting the strand and the side wire twisted outside thereof, and an end is formed in the internal gap. There is a problem that water and air enter from the part and corrode the PC strand.

[0004] In order to solve this problem, it has been proposed that, in the production of PC strands, each single strand thereof is coated with a synthetic resin in advance, twisted to form a strand, and further coated with a synthetic resin outside. (The actual opening 61-
144121).

[0005] However, since the conventional PC strand has not been subjected to the bluing treatment, there is a problem that the processing distortion of the material due to the twisting process remains, and it is easy to loosen and the strength is not stable. Because the entire circumference of the wire is separately covered, the synthetic resin layer is interposed between the core wire and the side wire, and when stretched, the synthetic resin layer is compressed and the interval between the wires is reduced, and the PC There was a problem that the elongation of the strand increased.

In order to solve such a problem, a PC strand in a completed state is used, and when the PC strand is passed through a synthetic resin extruder to apply a rust-proof coating, the molding machine is pressurized. A head is provided, and the inside of the head is
A technique has been developed in which the resin is pressed into the internal space of the PC strand by applying a pressure of about 00 kgf / cm ² or more, and a synthetic resin coating is applied to the entire outer periphery of the core wire and the outer side wire thereof ( JP-A-5-98742
No., Japanese Patent Application No. 5-37331).

[0007]

However, in the above-mentioned conventional rust-prevention treatment method by press-fitting a molten synthetic resin into a strand by pressurization, the molten synthetic resin material is inserted from the gap between the side wires to the outer periphery of the core wire. When the resin material has high viscosity and twisted strands with a high degree of bonding between the side wires, a large pressing force is required to press-fit, and the rust prevention capacity is limited. there were.

The above-mentioned conventional method is intended for a structure in which a single side wire is twisted around the outer periphery of a core wire.
This method cannot be applied to a multi-stranded PC strand in which a twisted side wire is formed as an intermediate layer and a plurality of outer layer wires are twisted on the outer side.

In view of such a conventional problem, the present invention is directed to a method of introducing a PC strand into a synthetic resin extruder and press-fitting a synthetic resin material to a central portion of the strand by pressurizing, whereby a lower load is applied. An object of the present invention is to provide a rust-proof PC strand and a rust-proof processing method which can be applied to a multi-strand PC strand, which can be rust-proof coated up to the inside by pressure, and can be applied to a multi-strand PC strand which could not be conventionally performed.

[0010]

The features of the rust-proof coated PC strand according to the present invention for solving the conventional problems as described above and achieving the intended object are as follows. ,
In a rust-preventive coated PC strand in which a rust-preventive coating layer made of a thermoplastic synthetic resin is adhered to the entire circumference of the above-described core wire and each side wire of a PC strand in which a number of side wires are twisted in a single layer, the outer periphery of the core wire The side wire is twisted in contact with
Is the diameter of the side wire and core wire of the PC strand, wherein in a state in which the lateral line is in contact with the core wire, the molten synthetic resin is easily possible flow into the gap until the core wire periphery between adjacent side tracks Secondly , a large number of middle-layer side wires are twisted in layers while being in contact with the outer periphery of the core wire , and the middle-layer side wires are formed.
The core wire outer periphery between said respective intermediate lateral line in of PC strands twisted into a layer form a plurality of outer side tracks outward, state the diameter of the middle side wire and core wire, each said middle lateral line is in contact with the core wire The rust-preventive coating layer made of a thermoplastic synthetic resin is adhered around each of the core wire and the side wire of each layer (claim 2). ).

[0011] Further, the feature of the rust-preventive coating method of the PC strand according to the present invention is as follows .
The side where each side wire is adjacent to the core wire, respectively.
Molten synthetic resin can easily flow into the outer circumference of the core wire between wires
To form an efficient gap and twist it into a single layer
The PC strand is passed through a synthetic resin extruder while being heated, and the thermoplastic synthetic resin material in a molten state is pressed from the gap between the respective side lines while being pressed by a pressing head of the synthetic resin extruder. The thermoplastic synthetic resin material is brought into close contact with the entire periphery of the core wire of the strand and each side wire by being pressed into the outer periphery of the core wire and extruding from a forming die at the tip of the pressure head (claim 3). , Many on the outer circumference of the core wire
, And each of the middle-layer side lines is in contact with the core wire.
In this state, the wire is melted to the outer circumference of the core wire between the middle side wires.
Creates a gap where the fused resin can easily flow in
Twisted, multiple outer layer side wires twisted in layers outside
The multi-strand PC strand thus formed is passed through a synthetic resin extruder while heating, and the thermoplastic synthetic resin material in a molten state while being pressed by a pressurizing head of the synthetic resin extruder is used for each of the above. Between each outer layer side line and each middle layer side line
There through the gap is pressed until the core periphery, to adhering the thermoplastic synthetic resin material on the entire circumference of the core wire and the side line of the strand by extruding from the pressurizing head tip forming die (claim 4) .

[0012]

In the present invention, since there is a gap between the side lines,
When this is passed through a synthetic resin extruder, the molten synthetic resin easily flows into the outer periphery of the core wire due to the pressurization of the pressurizing head. In addition, the PC strand is passed through the extruder while being heated, so that the flowability of the synthetic resin material is not reduced, the flow into the core wire is made smooth, and a strong adhesion is obtained after cooling and solidification. Can be

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 shows a first embodiment of a rust-proof coated PC strand according to the present invention.
Is a P consisting of one core wire 2 and six side wires 3,3 ...
It consists of a C strand 4 and a rust preventive material 5. The PC strands 4 are twisted in such a manner that side wires 3, 3... Also made of PC steel are spirally wound around the outer periphery of the core wire 2 made of PC steel. Each of the side wires 3, 3,... Is smaller in diameter than the core wire 2 so that when twisted around the core wire, a gap is formed between the side wires 3, 3,. Is molded.

FIG. 2 shows a second embodiment of the rust-proof coated PC strand 11 according to the present invention. This rust-proof coated PC strand 11 has nine middle side wires 1 outside a single core wire 12.
3 and 13 are twisted in a helical arrangement, and furthermore, a multiply stranded PC strand 15 in which nine outer layer side wires 14, 14. Also, the diameter of the middle layer side wires 13, 13,.
2 is formed in such a size that a gap is formed between the respective middle layer side lines 13, 13,....

As for the diameter of each wire of this multi-stranded PC strand, for example, in the case of a 19-stranded PC strand having a diameter of 21.8 mm, the following combinations can be made. (Unit m
m) In the first and second embodiments described above, the outer shape of the rust preventive material 5 is formed in a circular shape. However, as shown in FIGS. 6,1
6 may be formed.

Next, an embodiment of a rustproofing method according to the present invention will be described with reference to FIGS.

First, a strand material 2 composed of the PC strand 4 or 15 before the rustproof coating of the rustproof coated PC strand 1 or 11 as shown in FIGS.
3 (shown in FIG. 6 and FIG. 7) is placed on the feeding device 22 so that the PC strand material 23 can be continuously fed.

The PC strand material 23 is sequentially pulled out, and heated through an extruder 24 while being heated through a heating device 24.
Introduce to 5. This heating is maintained at a temperature of about 200 ° C.

As shown in FIG. 5, the extruder 25 has an auxiliary pressurizing head 27 connected to a tip of a crosshead 26 and a forming die 28 attached to the tip.

The PC strand material 23 heated through the heating device 24 is fed to the crosshead 2 of the extruder 25.
From 6, an auxiliary pressurizing head portion 27 and a forming die 28 at the tip end thereof are passed, and are joined to a leading wire (not shown) here. The leading wire is taken up by the take-up device 29 and wound around the leading wire reel 31 by the leading wire take-up device 30.

On the other hand, in the case of the present embodiment, the rust preventive material 5 made of a thermoplastic synthetic resin material is heated to about 200 ° C. by an extruder 25.
And is pressed into the auxiliary pressurizing head 27 from the crosshead 26. As the thermoplastic synthetic resin material, in addition to the polyethylene resin as described above, a polypropylene resin or a copolymer of polyethylene and polypropylene, a modified product thereof, and a synthetic resin such as a nylon resin can be used.

The auxiliary pressurizing head 27 connected to the crosshead 26 can be heated by a heater 32 so that the molten thermoplastic synthetic resin can flow into the PC strand material 23 without cooling. However, when the thermoplastic synthetic resin is an amorphous polymer having a low molecular weight, heating is not required.

The rust preventive material 5 made of a thermoplastic synthetic resin extruded into the cross head portion 26
Then, the PC strand material 23 is covered from the forming die 28 attached to the tip of the PC strand material 23. At this time, the resin pressure is increased to a certain level or more in the auxiliary pressing head portion 27, and the PC strand material 23 Is P shown in FIG.
In the case of C strand 4, gap a between side lines 3, 3 ...
The rust preventive material 5 in a molten state enters into the internal space b between the outer circumference of the core wire 2 and the side wires, and fills the internal space to form the side wire 3.
In addition, the outer periphery of the core wire 2 is covered.

When the PC strand material 23 is a multi-strand PC strand as shown in FIG.
The rust-preventive material 5 flows in from between 4, 14... And further reaches the outer periphery of the core wire 12 through the gap c between the middle side wires 13, 13.
Inner gap d between middle layer side line 13 and outer layer side line 14 and core wire 1
Fill the internal gap b between the wire 2 and the middle side line 13 and
All of the surfaces 3 and 14 are covered with the rust preventive material 5.

The resin pressure in the auxiliary pressurizing head 27 when each of the PC strand materials 23 is used is 80 to 100 kgf when the resin material is a polyethylene resin in the case of the PC strand material shown in FIG. / Cm ^2, and in the case of the multiply stranded PC strand material shown in FIG. 7, it is required to be 100 kgf / cm ² or more.

The length L ₂ of the auxiliary pressure head 27 is
It is longer than the forming die length L ₁ of the conventional crosshead portion. . This is L _{1 for} low molecular weight amorphous polymers.
Or at least twice the, it is desirable in the case of other thermoplastic synthetic resin is more than three times the L _1. And L ₁
In the case of 5 times or more, it is preferable to perform the drawing again through the forming auxiliary die 34. It exceeds 5 times L _1, only the die 28 swellings coating layer by overpressure, because prescribed outer layer is difficult to obtain.

As described above, the rust-proof coated PC strand covered with the rust-preventive material 5 made of a thermoplastic synthetic resin is extruded from the forming die 28 or, if necessary, the forming auxiliary die 34, and then passes through the cooling device 35. And cooled by the winding device 3
6 winds the reel 37. In the figure, reference numeral 39 denotes a pressure gauge.

After passing through the cooling device 35, the corona discharge machine 38 may be passed. In this method, corona discharge is applied in order to appropriately roughen the surface of the rust-proof coated PC strand particularly when adhesiveness to concrete is required.

As shown in FIGS. 1 and 2, the rust-preventive coated PC strand manufactured as described above has a rust-preventive coating layer completely adhered to the entire circumference of the core wire, the side wire and the outer layer wire. can get.

[0030]

As described above, according to the present invention, each side line is in contact with the core wire between the side lines or the middle layer side lines.
The molten synthetic resin fills the core wire between adjacent side wires.
By using a PC strand with a gap that allows easy inflow, the resin material that has been heated and melted can flow smoothly and uniformly when it passes through the head section under pressure conditions of a synthetic resin extrusion molding machine. As a result, a sufficient amount of the rust-preventive coating resin can be filled in the internal space even under low pressure conditions. It is possible to fill with rust coating resin.

[Brief description of the drawings]

FIG. 1 is a sectional view of a first embodiment of a rust-proof coated PC strand of the present invention.

FIG. 2 is a sectional view of the second embodiment.

FIGS. 3A and 3B are cross-sectional views of still another embodiment.

FIG. 4 is a diagram showing schematic steps of an example of the method of the present invention.

FIG. 5 is a cross-sectional view of the extruder of the above.

FIG. 6 is a cut end view of an example of a PC strand material used in the present invention.

FIG. 7 is a cut end view of another example of the above.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 11 Rust prevention coated PC strand 2, 12 core wire 3 side wire 4, 15 PC strand 5 Rust prevention material 6, 16 spiral groove 13 middle layer side line 14 outer layer side line 21 PC strand coil 22 unreeling device 23 strand material 24 heating device 25 extrusion Forming machine 26 Cross head part 27 Auxiliary pressurizing head 28 Forming die 29 Take-up device 30 Lead wire take-up device 31 Lead wire reel 32 Heater 34 Forming auxiliary die 35 Cooling device 36 Take-up device 37 Reel 38 Corona discharge machine 39 Pressure Total

────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yukihiro Higashi 1-14 Nagatano-cho, Fukuchiyama-shi, Kyoto Hien Electric Works Fukuchiyama Plant (56) References JP-A-4-111937 (JP, A) JP-A Heihei 5-163688 (JP, A) JP-A-4-241182 (JP, A) JP-A-60-13102 (JP, A) JP-A-7-90786 (JP, A) JP-A-55-33901 (JP, A) U) (58) Fields investigated (Int. Cl. ⁷ , DB name) D07B 1/00-9/00 E04C 5/08-5/10

Claims (4)

(57) [Claims] An anti-corrosion coating layer made of a thermoplastic synthetic resin is adhered to the entire periphery of the core wire and each side wire of a PC strand in which a number of side wires are twisted in a single layer around the outer periphery of the core wire. In the rust-coated PC strand, the side wires are twisted in contact with the outer periphery of the core wire.
Is the diameter of the side wire and core wire of the PC strand,
A rust preventive device characterized in that, in a state where each side wire is in contact with the core wire, a gap is formed between adjacent side wires so that a molten synthetic resin can easily flow into the outer periphery of the core wire. Coated PC strand. Numerous middle lateral line in a state of wherein contact with the outer periphery of the core wire
The PC strand many outer side line on the outside of the intermediate layer side wire twisted into a layer form with twisting in layers, the diameter of the middle side wire and core wire, wherein in a state where the middle side wire is in contact with the core wire A gap that allows the molten synthetic resin to easily flow into the outer periphery of the core wire is formed between each middle layer side wire, and a rust prevention coating layer made of a thermoplastic synthetic resin is adhered around each of the core wire and the side wire of each layer. Rust-proof coated PC strand. 3. A plurality of side lines are provided around the outer periphery of the core wire, and each side line is
Each of the cores is positioned between adjacent side wires in contact with the core.
Creates a gap through which molten synthetic resin can easily flow into the wire periphery
PC strand formed by twisting into a single layer
Is passed through a synthetic resin extruder while heating, and the thermoplastic synthetic resin material in a molten state while being pressurized by a pressurizing head of the synthetic resin extruder is used to remove the gap between the side lines.
A rust-preventive coated PC strand characterized in that a thermoplastic synthetic resin material is brought into close contact with the entire circumference of the core wire and each side wire of the strand by being press-fitted into the outer periphery of the core wire from the gap and extruding from a forming die at the tip of the pressure head. Rust prevention method. 4. A plurality of middle side wires around the outer periphery of the core wire,
Each middle layer side line in contact with each middle layer side
Molten synthetic resin easily flows into the outer circumference of the core wire between wires
Creates a possible gap and twists it in layers, on the outside
Multiple twists formed by twisting a number of outer layer side wires in layers
The PC strand, through a heated while synthetic resin extruder, the thermoplastic synthetic resin material in a molten state while being pressed by the pressure head portion of the synthetic resin extruder, wherein the outer
Wherein from between the layers surrounding wires is pressed to the core outer periphery through the gap between the middle side line, adhesion of the thermoplastic synthetic resin material on the entire circumference of the core wire and the side line of the strand by extruding from the pressurizing head tip forming die A rust-proofing method for a rust-proof coated PC strand, which is characterized in that: